Rotary electrical machines, as motors or generators, often incorporate a fan mounted on the rotor shaft to circulate air through the machine, cooling the electrical conductors and magnetic structure. Typically, the fans are stamped from metal as in Inagaki, U.S. Pat. Nos. 4,115,030 and 4,184,804, or molded as a unitary article from plastic, see Snider, U.S. Pat. No. 4,670,677. Such fans require expensive tooling.
A fan has been proposed having blades formed as discrete elements which are secured to the periphery of a carrier mounted on the rotor shaft of the machine or secured directly to the rotor itself. The blades may, for example, be molded from plastic. More particularly, the blade may be a simple panel, for example, mounted radially on the rotor. One form of such blade is a flat rectangular plate with a corner secured to a mounting plate at a joint, the blade extending at a right angle to the mounting plate. This blade is prone to fatigue failure at the joint because of its low natural frequency of vibration. The problem is partially relieved by the addition of a gusset.